Shift of absorption maximum towards shorter wavelength is called:

Question

Accepted Answer

The correct answer to the question "Shift of absorption maximum towards shorter wavelength is called:" is Option 3: Hypsochromic shift.

1. **Explanation for Option 3 (Hypsochromic shift):**
   - A hypsochromic shift, also known as a blue shift, refers to the movement of the absorption maximum of a substance towards shorter wavelengths in the electromagnetic spectrum. This shift typically occurs due to changes in the molecular environment, such as solvent effects, pH changes, or structural modifications that increase the energy gap between the ground and excited states of a molecule. As a result, the absorption maximum moves to a region of higher energy, which corresponds to shorter wavelengths.

2. **Explanation for why other options are incorrect:**

- **Option 1 (Hypochromic effect):**
     - The hypochromic effect refers to a decrease in the intensity (absorbance) of a spectral band without a shift in wavelength. It is not related to the position of the absorption maximum on the wavelength scale but rather to the magnitude of absorption. Therefore, it does not describe a shift towards shorter wavelengths.

- **Option 2 (Hyperchromic effect):**
     - The hyperchromic effect is the opposite of the hypochromic effect and involves an increase in the intensity (absorbance) of a spectral band. Like the hypochromic effect, it does not involve a shift in the wavelength of the absorption maximum. Thus, it is unrelated to the concept of shifting towards shorter wavelengths.

- **Option 4 (Bathochromic shift):**
     - A bathochromic shift, also known as a red shift, is the opposite of a hypsochromic shift. It refers to the movement of the absorption maximum towards longer wavelengths (lower energy). This shift occurs when the energy gap between the ground and excited states decreases, often due to similar factors that cause a hypsochromic shift but in the opposite direction. Therefore, a bathochromic shift does not describe a shift towards shorter wavelengths.

In conclusion, the term "hypsochromic shift" accurately describes the phenomenon of an absorption maximum moving towards shorter wavelengths, making Option 3 the correct answer.